Replacement: None. We do not currently have a replacement for this breakout but a revision is in the works. This page is for reference only.

This is a breakout board for the AD9835 signal generator chip from Analog devices. The AD9835 allows the user to make sine waves from 1Hz up to 25MHz with better than 1Hz resolution.

The breakout board has digital and analog supplies with separated ground planes, plus an SMA connector and 2-pin 0.1"-spaced header available for RF output. The output impedance is somewhat high (you can’t drive a speaker), so you may want to buffer the signal with an op amp.

We loved that kit too (I was asking around the building for one just the other day). Unfortunately, the chip at the heart of that kit was discontinued by the manufacturer, and without the chip, there’s no kit. We’re looking hard for a replacement, but so far everything else has been either too expensive or low quality. We’re still looking though!

Sorry for the confusion, the conversation split there. I was referring to our old function generator kit that was based around the Exar XR-2206, which has indeed shuffled off this mortal coil and joined the choir invisible. This breakout board’s retirement is a different issue; I believe because its performance wasn’t what we had hoped for. I don’t believe we have a replacement in development but I will check.

In the June 2011 QST magazine, there is an article describing this DDS chip used in a synthesizer for old Ham transmitters. The circuit uses a simple LT1253 amplifier to buffer the DDS output which would be useful to incorporate on this Sparkfun board. He uses a PIC16F877 controller, I would like to know if it is possible to duplicate the circuit and software with an Arduino instead.
There is a file of information at:
http://www.arrl.org/files/file/QST%20Binaries/Jun2011/QS0611Lunsford.zip
but you have to be a member to access.

At high frequencies, (~9MHz) the output looks pretty choppy on the oscilloscope. The frequency is probably still quartz accurate, but if you want something with low phase noise, this might not be a good LO choice.

The AD9835 Breakout Board (just like Analog Devices' own evaluation board for this chip) doesn’t have any filtering on its output. This lets you study the chip’s output spectrum, and try out filter designs that are optimized for some specific application. It’s common to use a low-pass filter with a corner frequency of about 30-40% of the DDS clock frequency, but sometimes you’ll do tricky stuff like deliberately filtering out the main output frequency and using one of the image frequencies.
Here are a couple of scope shots that I made. The first shows the unfiltered output of the board programmed for 10 MHz, and the second shows it with a 15 MHz low-pass filter (Mini-Circuits model SLP-15+). The yellow trace is the output signal, and the red trace is an FFT of the output signal.tek00000.png - unfilteredtek00001.png - 15 MHz LPF

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